1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor thin film, in particular, an indium antimonide thin film, and relates to a magnetoelectric conversion element provided with the semiconductor thin film manufactured by the aforementioned method.
2. Description of the Related Art
Hitherto, an indium antimonide, that is, InSb, compound semiconductor having high carrier mobility has been used as a material for magnetoelectric conversion elements, such as a magnetic resistance element and a hall element. Among those, for example, an InSb magnetic resistance element was made of an InSb single crystal bulk flake being adhered to a support substrate, and thereafter, being polished so as to be an element, although there was a problem of poor reliability at a high temperature. This was because of an occurrence of degradation in the adhesion force at a high temperature, an occurrence of peeling and cracks due to differences in thermal expansion coefficients among InSb, an adhesion layer, and a support substrate, etc. Therefore, in recent years, many attempts were made to directly grow semiconductor thin films of III-V compounds, such as InSb, on Si substrates, and an InSb thin film having good quality was produced as disclosed in Japanese Unexamined Patent Application Publication No. 7-249577. Since the InSb thin film having high quality was directly formed on the Si substrate so as to be an element, this film was a potential magnetic resistance material for high temperature uses, such as car electronics.
When the InSb thin film was grown on the Si substrate in accordance with the method disclosed in Japanese Unexamined Patent Application Publication No. 7-249577, however, the carrier mobility was about 42,000 cm2/Vxc2x7s or less, and was not sufficient for the desired sensitivity of the magnetic resistance element.
Accordingly, it is an object of the present invention to provide a method for manufacturing a semiconductor thin film having high carrier mobility. It is another object of the present invention to provide an electronic component, such as magnetoelectric conversion element, provided with the semiconductor thin film manufactured by the aforementioned method.
In order to achieve the aforementioned objects, a method for manufacturing a semiconductor thin film according to an aspect of the present invention is composed of the steps of removing a surface oxide film from a substrate having a surface made of a silicon single crystal hydrogen, terminating the surface of the substrate, forming a buffer layer made of indium on the substrate, forming an initial seed layer made of indium and antimony on the buffer layer, and forming a main growth layer made of indium and antimony on the initial seed layer while a temperature of the aforementioned substrate is kept at 460xc2x0 C. to 480xc2x0 C.
The step of removing the surface oxide film from the substrate having the surface made of the silicon single crystal and the step of hydrogen terminating the surface of the substrate are preferably performed at the same time with a treatment using an aqueous solution selected from the group consisting of an aqueous solution of hydrogen fluoride, an aqueous solution of ammonium fluoride, and a mixed aqueous solution thereof. Furthermore, in the formation of the main growth layer, it is preferable to raise a temperature of the substrate having the surface made of the silicon single crystal to 460xc2x0 C. to 480xc2x0 C., and to form the main growth layer after a retention time approximated by a function of the temperature of the substrate is provided.
According to the aforementioned method, the semiconductor thin film having high carrier mobility can be produced. More specifically, when the temperature T (xc2x0 C.) of the substrate having the surface made of the silicon single crystal is in the range of 460 to 480 (xc2x0 C.), and the retention time xcfx84 (min) satisfies the relationship represented by the formula xe2x88x920.02T2+17.3Txe2x88x923703 less than xcfx84 less than xe2x88x920.02T2+17.3Txe2x88x923691, a carrier mobility of 45,000 cm2/Vxc2x7s to 52,000 cm2/Vxc2x7s can be stably exhibited.
The method for manufacturing the semiconductor thin film according to the present invention is preferably further composed of the step of forming the main growth layer at a relatively low growth velocity so as to have a predetermined layer thickness, and the step of successively forming the main growth layer at a relatively high growth velocity. More specifically, it is preferable that the main growth layer is formed at a low growth velocity of 0.01 to 0.5 nm/s until the film thickness reaches 5 to 100 nm, and the main growth layer is successively formed at a high growth velocity of 0.2 to 5 nm/s.
According to the aforementioned method, in the process of forming the main growth layer, the crystallization property of InSb is improved by controlling the supply velocity of In and Sb at a low level in the initial stage of the main growth layer. After the layer thickness reaches the predetermined value, the InSb thin film can be successively formed at increased supply velocities of both materials without degradation of the crystallization property.
The step of removing the surface oxide film from the substrate having the surface made of the silicon single crystal and the step of hydrogen terminating the surface of the substrate are preferably performed with a treatment using an aqueous solution selected from the group consisting of an aqueous solution of hydrogen fluoride, an aqueous solution of ammonium fluoride, and a mixed aqueous solution thereof while the surface of the substrate is continuously exposed to the aforementioned aqueous solution in an activated state, so that all over the surface of the aforementioned substrate is uniformly hydrogen terminated.
In the formation of the buffer layer, the initial seed layer, and the main growth layer, it is preferable to heat and vaporize indium by an electron beam heating type vacuum evaporation method, and to deposit vaporized indium on the substrate having the surface made of the silicon single crystal.
Regarding an electronic component, such as magnetoelectric conversion element, according to another aspect of the present invention, the component includes a semiconductor thin film formed by the method of manufacture having the aforementioned features, and further includes at least one of a short circuit electrode, a terminal electrode, and a protection film, so that the component has sufficient reliability at a high temperature and has superior electrical properties.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.